The invention relates to a call back method in a communication system comprising one or more exchanges and a number of terminals (telephone sets, facsimile apparatuses, etc.) each of which being able to communicate through at least one of said exchanges with at least one of said other terminals, which method includes the performance of the following steps:
establishing a connection with a predetermined exchange
transmitting signals to the exchange indicating the number of the calling terminal, the number of the called terminal and the fact that the calling terminal has to be called back,
breaking the connection and wait for the exchange to establish the connection.
Such a method is described in WO9201350. Various embodiments of call back methods are described in this publication. The disadvantages will be described in the following. In general these prior art methods require significant effects from the user who has to be active during at least the first two of the above-indicated steps.
Such a system, in which use is made of the so-called call back procedure, is known as such for wire-bounded communication systems. The advantage of such systems is in many cases that the communication costs of the actual communication between the calling terminal and the desired terminal are calculated on the basis of date which will become available from the exchange which was involved in establishing the connection.
In general a number of exchanges are involved into establishing a connection, certainly if we are talking about trunk or international communication traffic. In general thereby the costs will be calculated by the first exchange in the series onto which the calling terminal is connected. That can be an exchange which calculates according to a relatively high tariff.
By making use of a call back procedure any arbitrary exchange anywhere in the world which preferably calculates according to a relatively low tariff, can be used for establishing the actual connection. Although sometimes contact has to be made with the call back exchange according to a relatively high tariff for a short while the timespan of this connection is very restricted. However, in many cases during establishing the connection use will be made only of signalling of which the costs are much lower or even nil.
A practical disadvantage of such a call back procedure is that to start with the user has to call the number of the call back exchange, has to wait thereafter until the call back exchange reports back and has to key in the number of the desired terminal thereafter. This procedure is very laborious. If automatic number callers are used this will lead to practical or sometimes even insurmountable problems.
It is sometimes possible by means of a predefined number translation to order the exchange directly to call a restricted number of predefined numbers. This, however, has the disadvantages that an extra manipulation (taking up the receiver) is still necessary, the number of items is restricted and always an appeal should be made to the memory of the caller to establish the correct connection.
In the mean time automatic call back diallers are developed for terminals in wire-bounded systems by means of which the above described manipulations can be automated. For wireless connections from a mobile terminal (mobile telephone, fax, modem, etc.) no corresponding solutions are known.
The purpose of the invention is now to indicate in which manner the system can be modified such that the user of a mobile terminal (among which are not comprised the terminals which in many home exchanges or company exchanges cooperate in a wireless manner with a fixed central station) is not confronted any more with the above-described laborious procedure, but, as in a wire-bounded system, only has to key in the number of the desired terminal to get a connection with said desired terminal.
In correspondence with the invention the system of the type as described in the first paragraph is characterized in that at least the calling terminals can be connected partly through wireless communication paths with their own exchange and do comprise a buffer in which the number of the desired other terminal can be stored, and comprise a circuit which, after said number is keyed in by the user and is stored in the said buffer,
performs the above-mentioned step a) instead of the user,
waits until the exchange reports again, retrieves the number from said buffer and transmits this number instead of the user to the exchange which will perform thereafter step d).
The added circuit according to the invention attends therefore to such a large part of the procedure that the only thing the user has to do is key in the number of the desired terminal.
According to a further development of the invention the circuit is furthermore capable to suppress the ringing signal which otherwise would sound when the connection is made by the exchange to the calling terminal.
Therewith the calling terminal acts in relation to the user as a conventional terminal and the user will not notice that a call back procedure is applied.
The invention not only relates to a whole system as above described but also relates to separate terminals. According to the invention the mobile terminal is characterized in that the terminal comprises a buffer in which the number of the desired other terminal is stored and comprises a circuit which, after said number is keyed in by the user and is stored in the buffer,
establishes the connection with the exchange,
reports as calling terminal,
after the connection is cut off waits until the exchange has established the connection again and retrieves the number from said buffer and transmits it to the exchange.
In many of the known mobile terminals use is made of a detachable module known as the SIM module or a therewith corresponding detachable unit in which a part of the electronic circuits (amongst others destined for identification purposes) is housed. It is found that the circuit, which according to the invention has to be added to the terminal to perform the above identified functions can be housed in this SIM module. This provides the possibility to adapt existing mobile terminals in a simple manner such that they can be applied in a communication system according to the invention.
In relation to the generally higher tariffs which apply for mobile communication over a wireless network (for instance GSM, Inmarsat, etc.) a suitable choice of the xe2x80x9ccall back exchangexe2x80x9d can lead to significant financial advantages.